1. Field of the Invention
The present invention relates to an air compression device mounted in an air compressor, and more particularly to an air compression device capable of adjusting exhaust timing of a valve so as to change an exhaust pressure.
2. Related Art
In a common air compressor, a set of air compression device is assembled to compress a gas drawn by the air compressor before the gas is exhausted. FIG. 1 is a schematic sectional view of a conventional air compression device. Referring to FIG. 1, an air chamber 101 is formed in an air compression device 10. A valve 102 is formed in the air chamber 101. The valve 102 is fixed, and is formed across an inner wall of the air chamber 101. A first rotor 1011 and a second rotor 1012 are assembled in the air chamber 101 respectively. When external air enters (as indicated by an arrow A in the figure), the first rotor 1011 and the second rotor 1012 are driven by an electric current to rotate synchronously. According to the figure, when the air just enters the air chamber 101, the first rotor 1011 is at the beginning of a stroke, and at this moment, the first rotor 1011 completely covers the valve 102. FIG. 2 is a schematic view of action of the conventional air compression device. Referring to FIG. 2, when the first rotor and the second rotor (1011, 1012) rotate, the air is gradually compressed to form compressed air A1, and after the first rotor 1011 rotates, the valve 102 covered by the first rotor 1011 is gradually exposed to be in an opened state to exhaust the compressed air A1 from the valve 102, so that through the action, air intake, compression, and exhaust strokes are completed continuously. Accordingly, after entering the air chamber 101, the external air is compressed by the two rotors (1011, 1012), so that before the air is exhausted, an exhaust pressure in the air chamber 101 increases gradually, an exhaust time point determines the exhaust pressure, and a motor power consumed by the two rotors increases as the exhaust pressure rises. However, the exhaust pressure, output power, and exhaust volume of a common rotor set are fixed. When a user needs a smaller exhaust volume, if the output motor power is high, energy is wasted; on the contrary, the exhaust may not be sufficient, which affects the efficiency of action of a connected mechanism. For example, when the air compression device is applied in an air intake system of a vehicle engine, since the difference between an exhaust volume required by a motorcar and an exhaust volume required by a locomotive is obviously large, in order to meet the demands of providing various exhaust volumes, multiple sets of the air compression devices are required, which greatly limits the application of the compressed air, and also leads to a high manufacturing cost.